The invention relates to oil reservoirs for hydraulic steering systems along the lines shown in German Patent DE-AS No. 1 750 715. Such reservoirs must be provided with a vent in order to prevent leakage of oil during extreme driving conditions, for example, a rough driving surface, centrifugal force in going around curves, a slanted position of the vehicle. The intrusion of splash or wash water into the oil reservoir housing must also be avoided. While the construction shown in the patent identified above has a labyrinth type screw lid for venting purposes which makes oil leakage difficult, it does not meet the requirements in full, in particular, when used in an all-terrain vehicle.
It has heretofore also been known in the prior art to secure a protective pipe to the lid of an oil reservoir for venting purposes, the pipe surrounding a bolt which extends between the lid and the oil reservoir housing to secure the two together. A relatively narrow protective pipe has an advantage in preventing oil moving about in the reservoir from reaching vent holes provided in the lid. Due to the relatively long protective pipe attached to the lid and the limited height in the engine compartment space in many cases, it is often very difficult to remove the lid in order to check the oil level.